Organic component's in soil mixes

[SpriteFish]

I've been doing lots of reading on past and current discussions on potting mixes e.g. soiless mixes, grit options, opinions of coco coir, etc. After reading all of those discussions I wanted to ask what people use as an organic component in mixes that require one e.g. soil mixes for succulents. I've seen some people use sphagnum moss (I'm unsure of the details in which this is used, so some insight would be great), I've also seen bark be highly recommend as an organic component (aside from its hydrophobic nature), and I've seen some people just use commercial potting mixes.

Another question I have regarding organic component's is about specific options, these questions are:
What sized bark is ideal for use in a potting mix?
And
What exactly do you look for in a commercial potting mix? I understand that large chunks of forest products is unideal but I was wondering if there was more details.

[MikeInOz]

New Zealand is where Orchiata bark comes from. They have a seedling grade (called ''Precision'') which is 3-6 mm. You can use that or you can use a potting mix which conforms to the Australian Standard - I'm sure they import it to NZ - and use a sieve to separate the various sizes, or you can use one manufactured there and recommended by the nursery industry. Or you can use cow manure which has been thoroughly decomposed (at least one year) then dried and screened. Or you can use a good quality commercial compost which is again dried and screened. Or you can use leaf mould gathered from under Nothofagus trees or deciduous trees and once again dried and screened. Composts, cow manure and leaf mould need to be wetted and solarized in a plastic bag in the sun on a hot day to bring them up to at least 60 degrees C for a couple of hours. This removes all pests and pathogens. A few weed seeds may survive. It should be mature, clean and free of sticks and other undecomposed material. pH should always be checked before use and adjusted to about 6.5 if needed.

[SpriteFish]

Hey, thank you for the list of options, this is exactly ehat I was looking for! I think orchid bark looks like a good option for now, and itd be worth me working on making my own compost (I saw your post on how to do it so I can go off that).

pH should always be checked before use and adjusted to about 6.5 if needed.

Speaking of soil pH, I was going to make a separate topic for this question but I suppose I might aswell ask this here. Could I have some form of basic guide to soil pH? E.g. Ideal pH, how to check it, what can unbalance it (I beleive fertilizers and water can affect it?). I think that's the last thing I need and then I'm confident I can make an appropriate soil mix for my plants.

[Steve Johnson]

New Zealand is where Orchiata bark comes from. They have a seedling grade (called ''Precision'') which is 3-6 mm. You can use that...

Only problem with any sort of tree bark is that it becomes hydrophobic after repeated wet-dry cycles. A wetting agent takes care of the problem, and I've read that yucca extract is a good one. We can find it here in the US, but I don't know about Australia and New Zealand. If yucca extract for plants isn't available there, would you recommend other wetting agents that'll work for growing cacti and succulents?

[SpriteFish]

I actually happen to know a New Zealand company that sells it so that'll work well! Do you have any instructions on how to use it? The site says "Use 1/16tsp (a pinch) to a 20L bucket as a peat moss wetting agent." But I'm not sure if you have more specific instructions for bark. (Note, it's in a powder form, I'm unsure if it has other forms but it's worth specifying.)

[MikeInOz]

New Zealand is where Orchiata bark comes from. They have a seedling grade (called ''Precision'') which is 3-6 mm. You can use that...

Only problem with any sort of tree bark is that it becomes hydrophobic after repeated wet-dry cycles. A wetting agent takes care of the problem, and I've read that yucca extract is a good one. We can find it here in the US, but I don't know about Australia and New Zealand. If yucca extract for plants isn't available there, would you recommend other wetting agents that'll work for growing cacti and succulents?

Yes. I use a commercial wetting agent. It's lasts the entire growing season. I would not recommend any of the organic types. Many have been found to not last long and to actually make things worse in some cases. I use it every year on many plants but still have not used it on cacti but I did notice some plants which were not potted for a while had difficulty absorbing water so next season I will try it out. It's important not to use too much and only do it once.
I use this. https://www.bunnings.com.au/amgrow-1l-w ... t_p3010119
I am sure there are similar products in the US

[MikeInOz]

Hey, thank you for the list of options, this is exactly ehat I was looking for! I think orchid bark looks like a good option for now, and itd be worth me working on making my own compost (I saw your post on how to do it so I can go off that).

pH should always be checked before use and adjusted to about 6.5 if needed.

Speaking of soil pH, I was going to make a separate topic for this question but I suppose I might aswell ask this here. Could I have some form of basic guide to soil pH? E.g. Ideal pH, how to check it, what can unbalance it (I beleive fertilizers and water can affect it?). I think that's the last thing I need and then I'm confident I can make an appropriate soil mix for my plants.

You need to find a soil pH test kit. If you use ammonium based fertilizers and have some limestone available in the mix, everything should work well. If you like nitrate for some reason, then you will need less lime or none depending on the water you use.
Be guided by how much lime to use by pH reading. It might take a couple of seasons to get the hang of what's going going the pot. Always let the appearance of the cactus be the final word.

[SpriteFish]

You need to find a soil pH test kit. If you use ammonium based fertilizers and have some limestone available in the mix, everything should work well. If you like nitrate for some reason, then you will need less lime or none depending on the water you use.
Be guided by how much lime to use by pH reading. It might take a couple of seasons to get the hang of what's going going the pot. Always let the appearance of the cactus be the final word.

I'll look at getting a soil pH test kit next time I'm out and about. I'm thinking that I'm going to use a fertilizer with a nitrate/ammonium ratio of 2:1 because i think thats what I saw recomended for potted cacti in one of the various posts about fertilizer.

I THINK my water is pretty much rain water, I may have to get it tested as im not 100% sure (My water is rainwater collected in a water tank, and as far as I know hasn't been treated in about half a decade).

Also in relation to wetting agents, I found two non-organic ones. One is granular and comes in a big 20kg bag (it's from the same company as the bark actually), and every other wetting agent seems to be lawn specific.

[Steve Johnson]

I'm thinking that I'm going to use a fertilizer with a nitrate/ammonium ratio of 2:1 because i think thats what I saw recomended for potted cacti in one of the various posts about fertilizer.

That was me, and it may be specific to pure soilless mineral mixes like my 60% pumice/40% granite gravel mix. The mix is essentially hydroponic, and this is something Mike said to me in another thread:

You mentioned that hydroponics uses mainly nitrate. That is simply because the media used in hydroponics has very low CEC (or none) and the risk of ammonium toxicity is much higher.

Very low CEC (cation exchange capacity) in pumice, none in granite. If you have soil in your mix, I'm thinking that a nitrate/ammonium ratio of 1:1 would be more appropriate assuming that the mix has relatively high CEC. Mike knows more about this than I do, so 1:1 is just a guess on my part.

[Steve Johnson]

We shouldn't make any assumptions about what our members do or don't know, so for those of you who don't know about CEC, we'll dig into it (pun intended)...

From Ohio State University Extension (https://ohioline.osu.edu/factsheet/anr-81):

• "Cation exchange capacity (CEC) is a fundamental soil property used to predict plant nutrient availability and retention in the soil. It is the potential of available nutrient supply, not a direct measurement of available nutrients. Soil CEC typically increases as clay content and organic matter increase because cation exchange occurs on surfaces of clay minerals, organic matter, and roots. Soils in Ohio can encompass a wide CEC range, but typically fall somewhere between 5 to 25 meq/100 g soil (Table 1). Values over 25 meq/100 g soil are found with heavy clay soils, organic, or muck soils."

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• "Calculating CEC from a Soil Test
  
  "CEC is reported as milliequivalents per 100 grams of soil (meq/100g), or charge per weight of soil. Milliequivalents are used instead of weight because charge is more useful when talking about ion exchange.
  
  "So, how do we take the concentration of nutrients in a soil test (ppm) and convert to charges (meq/100g soil)? Soil testing laboratories often provide these values already on the soil test report, or will provide them upon request."

Not sure that we need to go so far as to pay for a soil test done by a test lab, but that's your choice (last time I checked, soil tests here in the US run into the hundreds of dollars).

I used to think that a lot of commercial potting soils are garbage because they're way too rich in organic matter for cacti. Mike corrected me (and by extension our other members) when he said this:

Organic material does NOT cause disease of any kind. Pathogenic organisms do. Pathogens do not ''come with'' organic material. They are everywhere including the computer screen you are looking at right now, all over your clothes and even in the dust in the air. All they need is food and the correct environment...So what is the problem with organic? Well it breaks down and as it does, water holding capacity goes up and air-filled porosity goes down. That can benefit some (but not all) pathogens. It is the same as using very fine mineral components to the mix. Therefore, using organic materials will be more acceptable for... plants which can tolerate slower drying in the mix (eventually), small pots, watering frequency which is low. Organic materials will be less acceptable for plants which do not like slowly increasing water holding capacity, large pots and watering frequency which is high.

For soil-based mixes, it appears that organic soils are actually the best fit with the mineral component in the mix -- and if that's the case, maybe commercial potting soils aren't so bad after all. The trick will be to find the correct proportions of mineral gravel and soil. That's up to individual growers, their local climates, and what they're growing. The only problem I see with soil-based mixes -- water-holding capacity increases to unacceptable levels if the mix isn't periodically changed out with fresh mix. How often? That I can't tell you, but from what I've heard over the years, most growers repot their cacti with fresh mix every 2-3 years.

Question for you, Mike -- if growers are using soil-based mixes, would a 1:1 ammonium-to-nitrate ratio be okay, or would you recommend tilting more in favor of ammonium N in the fertilizer? I also have another one that makes me question my belief that a 1:2 ammonium-to-nitrate ratio is suitable for a hydroponic mix like the pumice and granite gravel mix I'm using:

Another is that Nitrate ions tend to be preferred in hotter conditions.

The other way round I believe. A level of ammonium which is completely safe during the bright and warm summer can be quite toxic in winter due to the lack of photosynthate production leading to ammonium toxicity. Traditionally, nitrate is seen as a '' low temp, low light winter'' fertilizer of preference in greenhouse production.

The growing season here in SoCal ends around the middle of October, so I stop watering before then. I also give the collection its last deep watering of the year with plenty of Ca and no fertilizer (that's a good tip I got from you -- thanks!). While overnight lows cool off down to the 40s (Fahrenheit) starting around late October/early November, there are plenty of hot days even into December. If I supplement the fert with a touch of urea to give me a 1:1 ratio, would that be better or do you think that ammonium toxicity is still a risk? If you say the touch of urea is helpful, I know how to do it by adding it to my ammonium sulfate-potassium sulfate stock solution.

[MikeInOz]

Hi Steve

Regarding the ammonium to nitrate ratios, rather than going into a long reply, I will post a couple of pages from my text book regarding ammonium toxicity. Hopefully you can read them. I'm happy to discuss more after that but I would say that there is little chance of ammonium toxicity in your situation even at a 1 to 1 ratio because 1/ you don't feed in winter and 2/ the concentrations of your fertilizers are quite low. The ammonium to nitrate ratio of the osmocote I use is 2.13! No problems at all with that.

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[Steve Johnson]

Hi Steve

Regarding the ammonium to nitrate ratios, rather than going into a long reply, I will post a couple of pages from my text book regarding ammonium toxicity. Hopefully you can read them. I'm happy to discuss more after that but I would say that there is little chance of ammonium toxicity in your situation even at a 1 to 1 ratio because 1/ you don't feed in winter and 2/ the concentrations of your fertilizers are quite low. The ammonium to nitrate ratio of the osmocote I use is 2.13! No problems at all with that.

Hi Mike,

I downloaded those pages as jpegs, so I have them archived for future use. What you said is what I was hoping for -- I'll readjust my fertilizer recipe for a 1:1 ratio. Urea will be required to make it happen, which gives me a couple of options I detailed in the PM I sent you:

• Option #1. Add a touch of urea to my ammonium sulfate-potassium sulfate stock solution. Dilute 6 fluid ounces per gallon of watering solution -- that'll give me 17 ppm ammonium N, 14 ppm urea N, and 31 ppm nitrate N. 62 ppm total N per feeding, IMO quite acceptable.

• Option #2. Ditch the ammonium sulfate and go with a urea-potassium sulfate stock solution. Dilute 6 fluid ounces per gallon of watering solution -- that'll give me 2 ppm ammonium N (the scant amount I get from my General Hydroponics 5-0-1), 29 ppm urea N, and 31 ppm nitrate N. My current watering solution includes 38 ppm S, which might be higher than I'd like, so this option would bring the S down to about 19 ppm per feeding. By the way -- I know that S toxicity is rare, but more of a risk in hydroponics. Will 19 ppm S be enough and sufficient to eliminate the risk?

Since I'll be adding urea to the nutrient mix, I'm mindful of this:

Btw - what role does urea nitrogen play and is ammoniacal superior because it removes one more step of conversion through hydrolysis?

Urea can be taken up by plants directly and they use the enzyme urease to convert it to ammonium. Nickel is required in this process. Urea is also converted to ammonium (and finally nitrate) within about 2 days in the pot.

For the most efficient urea-ammonium conversion, I would add nickel sulfate to my sodium molybdate stock solution. To spare you the math exercise involved, I'll just state that what I'll have in the watering solution is 0.053 ppm Mo and about the same amount of Ni per feeding. I can buy 49-0-0 urea and nickel sulfate online. Calculating the right amounts for the stock solutions is easy, and it's simply a matter of choosing the option that works best for my cacti over the long run. Mike, will option #2 be more effective? And would you foresee a toxicity problem with the amount of Ni I have in mind?

[MikeInOz]

I downloaded those pages as jpegs, so I have them archived for future use. What you said is what I was hoping for -- I'll readjust my fertilizer recipe for a 1:1 ratio. Urea will be required to make it happen, which gives me a couple of options I detailed in the PM I sent you:

• Option #1. Add a touch of urea to my ammonium sulfate-potassium sulfate stock solution. Dilute 6 fluid ounces per gallon of watering solution -- that'll give me 17 ppm ammonium N, 14 ppm urea N, and 31 ppm nitrate N. 62 ppm total N per feeding, IMO quite acceptable.

That looks perfectly acceptable to me.

Option #2. Ditch the ammonium sulfate and go with a urea-potassium sulfate stock solution. Dilute 6 fluid ounces per gallon of watering solution -- that'll give me 2 ppm ammonium N (the scant amount I get from my General Hydroponics 5-0-1), 29 ppm urea N, and 31 ppm nitrate N. My current watering solution includes 38 ppm S, which might be higher than I'd like, so this option would bring the S down to about 19 ppm per feeding. By the way -- I know that S toxicity is rare, but more of a risk in hydroponics. Will 19 ppm S be enough and sufficient to eliminate the risk?

That is also fine. I don't know much about S toxicity but you won't have any problems with 19ppm for sure.

For the most efficient urea-ammonium conversion, I would add nickel sulfate to my sodium molybdate stock solution. To spare you the math exercise involved, I'll just state that what I'll have in the watering solution is 0.053 ppm Mo and about the same amount of Ni per feeding. I can buy 49-0-0 urea and nickel sulfate online. Calculating the right amounts for the stock solutions is easy, and it's simply a matter of choosing the option that works best for my cacti over the long run. Mike, will option #2 be more effective? And would you foresee a toxicity problem with the amount of Ni I have in mind?

I don't think nickel deficiency has even been well documented it's so rare. Most people don't even include it. If you use soil at all you probably won't need it. In hydroponics with urea N it's probably a good idea to include some. 0.05ppm is fine and probably even half that would be ok. But you should not have toxicities of any of the metals unless your pH drifts way down to about 5 and then only if there is too much in the mix. Boron is usually the first to show up. I can't honestly say I have ever seen a case of toxicity from fertilizer ever! But I have certainly seen deficiencies all over the place.

[Steve Johnson]

I downloaded those pages as jpegs, so I have them archived for future use. What you said is what I was hoping for -- I'll readjust my fertilizer recipe for a 1:1 ratio. Urea will be required to make it happen, which gives me a couple of options I detailed in the PM I sent you:

• Option #1. Add a touch of urea to my ammonium sulfate-potassium sulfate stock solution. Dilute 6 fluid ounces per gallon of watering solution -- that'll give me 17 ppm ammonium N, 14 ppm urea N, and 31 ppm nitrate N. 62 ppm total N per feeding, IMO quite acceptable.

That looks perfectly acceptable to me.

Option #2. Ditch the ammonium sulfate and go with a urea-potassium sulfate stock solution. Dilute 6 fluid ounces per gallon of watering solution -- that'll give me 2 ppm ammonium N (the scant amount I get from my General Hydroponics 5-0-1), 29 ppm urea N, and 31 ppm nitrate N. My current watering solution includes 38 ppm S, which might be higher than I'd like, so this option would bring the S down to about 19 ppm per feeding. By the way -- I know that S toxicity is rare, but more of a risk in hydroponics. Will 19 ppm S be enough and sufficient to eliminate the risk?

That is also fine. I don't know much about S toxicity but you won't have any problems with 19ppm for sure.

For the most efficient urea-ammonium conversion, I would add nickel sulfate to my sodium molybdate stock solution. To spare you the math exercise involved, I'll just state that what I'll have in the watering solution is 0.053 ppm Mo and about the same amount of Ni per feeding. I can buy 49-0-0 urea and nickel sulfate online. Calculating the right amounts for the stock solutions is easy, and it's simply a matter of choosing the option that works best for my cacti over the long run. Mike, will option #2 be more effective? And would you foresee a toxicity problem with the amount of Ni I have in mind?

I don't think nickel deficiency has even been well documented it's so rare. Most people don't even include it. If you use soil at all you probably won't need it. In hydroponics with urea N it's probably a good idea to include some. 0.05ppm is fine and probably even half that would be ok. But you should not have toxicities of any of the metals unless your pH drifts way down to about 5 and then only if there is too much in the mix. Boron is usually the first to show up. I can't honestly say I have ever seen a case of toxicity from fertilizer ever! But I have certainly seen deficiencies all over the place.

Well, Mike, where would I be without you? I'm very strict about not letting the final pH of my watering solution go below 6.0 when I acidify the tap water after I add in the ferts and supplements, so I'll be fine with everything. I can't thank you enough for helping all of us.

[SpriteFish]

I used to think that a lot of commercial potting soils are garbage because they're way too rich in organic matter for cacti. Mike corrected me (and by extension our other members) when he said this:

Organic material does NOT cause disease of any kind. Pathogenic organisms do. Pathogens do not ''come with'' organic material. They are everywhere including the computer screen you are looking at right now, all over your clothes and even in the dust in the air. All they need is food and the correct environment...So what is the problem with organic? Well it breaks down and as it does, water holding capacity goes up and air-filled porosity goes down. That can benefit some (but not all) pathogens. It is the same as using very fine mineral components to the mix. Therefore, using organic materials will be more acceptable for... plants which can tolerate slower drying in the mix (eventually), small pots, watering frequency which is low. Organic materials will be less acceptable for plants which do not like slowly increasing water holding capacity, large pots and watering frequency which is high.

For soil-based mixes, it appears that organic soils are actually the best fit with the mineral component in the mix -- and if that's the case, maybe commercial potting soils aren't so bad after all. The trick will be to find the correct proportions of mineral gravel and soil. That's up to individual growers, their local climates, and what they're growing. The only problem I see with soil-based mixes -- water-holding capacity increases to unacceptable levels if the mix isn't periodically changed out with fresh mix. How often? That I can't tell you, but from what I've heard over the years, most growers repot their cacti with fresh mix every 2-3 years.

What are the pros and cons of loam (commercial potting soil), bark, and compost? I might aswell ask so I can compare them!
I was just thinking that soil might be more versatile than bark, as I can add it to any mix and adjust the pumice:soil ratio depending on the plant species. Also I was wondering if prehaphs one was less hydrophobic than the other.